
//https://dart.cn/language/extend/#overriding-members
class Television {
  // ···
  set contrast(int value) {
   
  }
}

class SmartTelevision extends Television {
  @override
  set contrast(num value) {
    
  }
  // ···
}


//https://dart.cn/language/extend/#nosuchmethod
class A {
  // Unless you override noSuchMethod, using a
  // non-existent member results in a NoSuchMethodError.
  @override
  void noSuchMethod(Invocation invocation) {
    print(
      'You tried to use a non-existent member: '
      '${invocation.memberName}',
    );
  }
}